Three dimensional imaging system

ABSTRACT

Recent advances in surface techniques have lead to the development of extremely small (sub-micron) scale features. These techniques allow the formation of polymer micro-lenses as well as variable focus liquid lenses. The present invention primarily concerns the use of small scale lenses for the fabrication of novel displays which exhibit three-dimensional (3D) effects. Both still images and video images (or other motion images) can be generated.

FIELD OF THE INVENTION

[0001] The present invention relates generally to optical systems, andmore specifically to three dimensional imaging systems incorporatingdiffractive, refractive, or diffractive/refractive compound lenses.

BACKGROUND Human Vision

[0002] Normal human vision provides a perception of space in the visualfield of view that is in color and three dimensions (3D). A betterrealization of the optical requirements for a photographic system topresent an acceptable 3D stereoscopic image or stereo-model to theviewer is given by an understanding of stereopsis, or visual perceptionof space.

[0003] The stimulus conditions for space perception are termed cues, andare in two groups. The monocular group allows stereopsis with one eyeand includes relative sizes of subjects, their interposition, linear andaerial perspective, distribution of light and shade, movement parallaxof subject and background and visual accommodation. The binocular groupuses the two coordinated activities of both eyes: firstly, visualconvergence, where the optical axes converge muscularly from parallelfor distant vision to a convergence angle of 23° for a near point of 150mm; and secondly, stereoscopic vision, where, due to the two differentvisual viewpoints, the imaging geometry gives two disparate retinalimages for the left and right eyes. The disparities are due to parallax,the relative displacement of corresponding or homologous image points ofa subject point away from the optical axis due to its position in thebinocular field of view.

[0004] Retinal images are encoded for transmission as frequencymodulated voltage impulses along the optic nerve, with signal processingtaking place at the intermediate lateral geniculate bodies and then thevisual cortex of the brain. The resultant visual perception is unique tothe observer. For a further discussion of human 3D perception, see,e.g., Sidney F. Ray, “Applied Photographic Optics Imaging Systems ForPhotography, Film and Video,” Focal Press, pp. 469-484, (1988), which isincorporated herein by reference.

3D Techniques

[0005] Many prior art 3D imaging systems use parallax to generate the 3Deffect. Section 65.5 of Ray, cited above and which is incorporatedherein by reference, provides a good description of severalparallax-based techniques, such as 3D movies, stereo viewing of twoside-by-side offset images, 3D post cards, etc. Although theseparallax-only based systems offer some degree of 3D effect, they arediscernably unrealistic.

[0006] Another well known, but far more complex technique for generating3D images is holography. While holography can produce quite realistic 3Dimages, its use is quite limited because of the need for coherent lightsources (such as lasers) and the darkroom or near darkroom conditionsrequired to generate holograms.

[0007] One prior art technique for generating 3D images, known asintegral photography, uses an array of small lenses (referred to as afly's eye lens or a micro-lens array) to both generate and reproduce 3Dimages. The technique of integral photography is described in Ives,Herbert E., “Optical Properties of a Lippmann Lenticulated Sheet,”Journal of the Optical Society of America 21(3):171-176 (1931).

[0008] Other techniques incorporating micro-lens arrays for thegeneration of 3D images are described in Yang et al., 1988, “Discussionof the Optics of a New 3-D Imaging System,” Applied Optics27(21):4529-4534; Davies et al., 1988, “Three-Dimensional ImagingSystems: A New Development,” Applied Optics 27(21):4520-4528; Davies etal., 1994, “Design and Analysis of an Image Transfer System UsingMicro-lens Arrays,” Optical Engineering 33(11):3624-3633; Benton,Stephen A., 1972, “Direct Orthoscopic Stereo Panoramagram Camera,” U.S.Pat. No. 3,657,981; Nims et al., 1974, “Three Dimensional Pictures andMethod of Composing Them,” U.S. Pat. No. 3,852,787; and Davies et al.,1991, “Imaging System,” U.S. Pat. No. 5,040,871, each of which isincorporated herein by reference. A drawback of the above micro-lensarray based 3D optical systems is that all lenses in the array have afixed focal length. This greatly limits the type of 3D effects that canbe generated by such arrays.

The Fabrication of Micro-lens Arrays

[0009] Great advances in the generation of very small scale surfacefeatures have been made recently. Micro-stamping techniques using selfassembling monolayers (SAMs) have allowed low cost production offeatures on sub-micron (<10⁻⁶ m) scales.

[0010] Certain compounds, when placed in an appropriate environment, arecapable of spontaneously forming an ordered two dimensional crystallinearray. For example, solutions of alkane thiols exhibit this property ongold. Micro-stamping or micro contact printing uses a ‘rubber’ (siliconeelastomer) stamp to selectively deposit alkane thiols in small domainson gold surfaces. A ‘master’ mold with the desired feature shapes andsizes is fabricated using optical lithographic techniques well known inthe electronic arts. Poly(dimethylsiloxane) (PDMS), a siliconeelastomer, is poured over the master and allowed to cure and then gentlyremoved. The resulting stamp is then inked by brushing the PDMS surfacewith a solution of the appropriate alkane thiol. The PDMS stamp is thenplaced on a gold surface and the desired pattern of alkane thiols isdeposited selectively as a monolayer on the surface. The monolayers maybe derivatized with various head groups (exposed to the environment awayfrom the metallic surface) in order to tailor the properties of thesurface.

[0011] In this fashion, alternating domains, hydrophilic andhydrophobic, may be easily fabricated on a surface on a very smallscale. Under appropriate conditions, such a surface, when cooled in thepresence of water vapor, will selectively condense water droplets on thehydrophilic surface domains. Such droplets can act as convergent ordivergent micro-lenses. Any shape lens or lens element may be produced.SAMs may be selectively deposited on planar or curved surfaces which mayor may not be optically transparent. Offsetting, adjacent, stacked, andother configurations of SAM surfaces may all be used to generate complexlens shapes.

[0012] Using techniques similar to the SAM techniques discussed above,transparent polymers have been used to make stable micro-lenses. Forexample, a solution of unpolymerized monomers (which are hydrophilic)will selectively adsorb to hydrophilic domains on a derivatized SAMsurface. At that point, polymerization may be initiated (e.g., byheating). By varying the shape of the derivatized surface domains, theamount of solution on the domain, and the solution composition, a greatvariety of different lenses with different optical properties may beformed.

[0013] For examples of optical techniques incorporating liquid opticalelements and SAMs, see Kumar et al., 1994, “Patterned CondensationFigures as Optical Diffraction Gratings,” Science 263:60-62; Kumar etal., 1993, “Features of Gold Having Micrometer to Centimeter DimensionsCan be Formed Through a Combination of Stamping With an ElastomericStamp and an Alkanethiol ‘Ink’ Followed by Chemical Etching,” Appl.Phys. Lett. 63(14):2002-2004; Kumar et al., 1994, “PatterningSelf-Assembled Monolayers: Applications in Materials Science,” Langmuir10(5):1498-1511; Chaudhury et al., 1992, “How to Make Water Run Uphill,”Science 256:1539-1541; Abbott et al., 1994, “Potential-Dependent Wettingof Aqueous Solutions on Self-Assembled Monolayers Formed From15-(Ferrocenylcarbonyl)pentadecanethiol on Gold,” Langmuir10(5):1493-1497; and Gorman et al., in press, “Control of the Shape ofLiquid Lenses on a Modified Gold Surface Using an Applied ElectricalPotential Across a Self-Assembled Monolayer,” Harvard University,Department of Chemistry, each of which is incorporated herein byreference.

[0014] Micro-lens arrays can also be fabricated using several other wellknown techniques. Some illustrative techniques for the generation ofmicro-lens or micromirror arrays are disclosed in the followingarticles, each of which is incorporated herein by reference: Liau etal., 1994, “Large-Numerical-Aperture Micro-lens Fabrication by One-StepEtching and Mass-Transport Smoothing,” Appl. Phys. Lett.64(12):1484-1486; Jay et al., 1994, “Preshaping Photoresist forRefractive Micro-lens Fabrication,” Optical Engineering33(11):3552-3555; MacFarlane et al., 1994, “Microjet Fabrication ofMicro-lens Arrays,” IEEE Photonics Technology Letters 6(9):1112-1114;Stern et al., 1994, “Dry Etching for Coherent Refractive Micro-lensArrays,” Optical Engineering 33(11):3547-3551; and Kendall et al., 1994,“Micromirror Arrays Using KOH:H₂O Micromachining of Silicon for LensTemplates, Geodesic Lenses, and Other Applications,” Optical Engineering33(11):3578-3588.

Focal Length Variation and Control

[0015] Using the micro-stamping technique discussed above, small lensesmay be fabricated with variable focal lengths. Variable focus may beachieved through several general means, e.g., (i) through the use ofelectrical potentials; (ii) through mechanical deformation; (iii)through selective deposition, such as deposition of liquid water dropsfrom the vapor phase (as described in Kumar et al., (Science, 1994)cited above); and (iv) heating or melting (e.g., structures may bemelted to change optical properties, as in some micro-lens arrays whichare crudely molded and then melted into finer optical elements).

[0016] The degree to which a solution wets or spreads on a surface maybe controlled by varying the electronic properties of the system. Forexample, by placing microelectrodes within the liquid lens and varyingthe potential with respect to the surface, the curvature of the lens maybe varied. See Abbott et al, cited above. In other configurations,hydrophobic liquid micro-lenses are formed on a surface and covered withan aqueous solution and the surface potential is varied versus theaqueous solution. Such systems have demonstrated extremely small volumelenses (1 nL) which are capable of reversibly and rapidly varying focus(see Gorman et al., cited above).

[0017] Referring now to FIG. 3, a schematic diagram of a variable focuslens 50 is shown. Variable focus lens 50 includes a liquid lens 52 andtwo SAM surfaces 54. SAM surfaces 54 adhere to liquid lens 52. As can beseen in the progression from FIGS. 3(a) through 3(c), by varying thedistance between the SAM surfaces 54, the shape, and therefore opticalcharacteristics, of liquid lens 52 can be altered. There are alsoseveral other ways to vary the shape and optical characteristics ofliquid lens 52. For example, the electrical potential between lens 52and surface 54 can be varied, causing changes in the shape of lens 52,as is discussed further below with respect to FIG. 4. The index ofrefraction of lens 52 can be varied by using different liquid materials.The cohesive and adhesive properties of liquid lens 52 can be adjustedby varying the chemistry of the liquid material, and by varying thechemistry of surface 54. The three dimensional characteristics ofsurface 54 can be varied. For example, when viewed from the top orbottom surface 54 can be circular, rectangular, hexagonal, or any othershape, and may be moved up and down. These techniques may be usedindividually or in combination to create a variety of lens shapes andoptical effects.

[0018] Referring now to FIG. 4, a schematic diagram of an electricallyvariable focus lens as disclosed in the above cited Abbott et al.article is shown. A drop of liquid 52 is placed on SAM surface 54, whichis in turn formed on metallic surface 56, preferably gold. By varyingthe electric potential between microelectrode 58 and SAM surface 54, thecurvature (and thus optical characteristics) of liquid lens 52 can bevaried. The progression from FIG. 4(a) to 4(c) shows schematically howthe shape of liquid lens 52 can be changed. Similar effects can beachieved using the techniques described in the above Gorman et al.article, although microelectrodes 58 need not be used.

[0019] Alternatively, such micro-lenses may be focused throughmechanical means. For example, flexible polymeric or elastomeric lensesmay be compressed or relaxed so as to vary focus through piezoelectricmeans. Alternatively, liquid lenses encapsulated in flexible casings maybe mechanically compressed or relaxed.

SUMMARY OF THE INVENTION

[0020] The present invention provides a 3D optical system which, incontrast to the prior art, includes a variable focus micro-lens arrayand an image that appears to have been taken with an optical systemhaving a relatively high depth of field; that is, objects of varyingdistances within the image are substantially in focus over apredetermined area. In an alternative embodiment, variable focusmicro-lens arrays can be used in combination with still or motion imagesto cause the apparent distance of the image to change. Anotherembodiment uses fixed arrays having elements with varying focal lengthsto create 3D and other optical effects.

DESCRIPTION OF THE FIGURES

[0021]FIG. 1 is a schematic diagram showing a 3D imaging systemincorporating a micro-lens array according to a preferred embodiment.

[0022] FIGS. 2(a)-2(c) are schematic diagrams showing the path of lightdirected to an observer under various conditions.

[0023] FIGS. 3(a)-3(c) are schematic diagrams showing one technique forvarying the focal length of a liquid micro-lens through the use of SAMs.

[0024] FIGS. 4(a)-4(c) are schematic diagrams showing another techniquefor varying the focal length of a liquid micro-lens through the use ofSAMs.

[0025]FIG. 5 is a block diagram of a camera used to make two dimensionalimages of the type used in a preferred embodiment.

DETAILED DESCRIPTION

[0026] The structure and function of the preferred embodiments can bestbe understood by reference to the drawings. The reader will note thatthe same reference numerals appear in multiple figures. Where this isthe case, the numerals refer to the same or corresponding structure. Ina preferred embodiment, variable focus micro-lens arrays, such as thosefabricated using the techniques discussed above, along with still ormotion images having relatively great depth of field, are used to create3D effects.

[0027] Referring to FIG. 2(a), images viewed by the human eye comprise aplurality of extremely fine points which are perceived in continuousdetail. As light falls on each object point, the light is scattered andthe point diffusely reflects a cone of light 30 (i.e., light whichsubtends some solid angle) outward. If an object is viewed at aconsiderable distance, by an observer 20, then a very small portion ofcone 30 is collected; and the rays of light that are collected arenearly parallel (see FIG. 2(a): far focus). As the viewing distancedecreases, however, the rays collected by the eyes of observer 20 areless parallel and are received at greater diverging angles (see FIG.2(a); medium focus and close focus). The complex of the cornea andlenses changes shape so that objects at varying distances can befocused. For a more complete discussion of diffuse reflection of thetype discussed above, see, e.g., Tipler, Paul A., Physics for Scientistsand Engineers, Third Edition, Extended Version, Worth Publishers, pp.982-984, which is incorporated herein by reference.

[0028] According to a preferred embodiment, a two dimensional photographor image which is in focus at all points of the image is overlaid withan array of micro-lenses. With proper illumination, such a system cangenerate light cones of varying divergence and simulate 3D space.

[0029] Because photographic lenses only have one primary point of focus,there is only one plane in the photograph which is in exact focus; infront of and behind this plane the image is progressively out of focus.This effect can be reduced by increasing the depth of field, but canonly be corrected to a certain extent.

[0030] In general, a preferred embodiment of the present invention willwork with images generated using an optical system having a large depthof field. For certain images, proper placement of the plane of focus anduse of depth of field is adequate to attain perceived sharpnessthroughout the entire image. In other situations, more advancedtechniques are required to attain perceived exact focus for all pointswithin an image. Modified cameras and/or digital imaging techniques maybe used. For example, some out of focus areas within an image may befocused using digital software ‘sharpening’ filters.

[0031] Referring now to FIG. 5, a block diagram of a camera 60 used tomake two dimensional images of the type used in a preferred embodimentis shown. Camera 60 includes conventional motorized optics 62 having aninput lens 64 and an output lens 66. While lenses 64 and 66 have beendepicted as convex lenses, those skilled in the art will understand thatlenses 64 and 66 may be of any desired configuration. Motorized optics62 focuses an image on image recorder 72. An image can also be focusedon image recorder 72 by varying the distance between image recorder 72and output lens 66 either independently, or in combination withadjustments in motorized optics 62. Image recorder 72 may be a chargecoupled device (CCD), photomultiplier tube (PMT), photodiode, avalanchephotodiode, photographic film, plates, or other light sensitivematerials. In addition, image recorder 72 may be a combination of any ofthe above light recording or collecting devices.

[0032] The focus of motorized optics 62 is controlled by controller 68,which is coupled to motorized optics 62 via control line 70. Controller68 may be a microprocessor, micro-controller, or any other device whichgenerates a digital or analog signal that can be used to control thefocus of motorized optics 70.

[0033] If image recorder 72 is a digital device, then images captured byimage recorder 72 are stored in memory 74. If image recorder 72 is aphotographic or light sensitive material, then memory 74 is not needed.

[0034] Memory 74 may be semiconductor memory, magnetic memory, opticalmemory, or any other type of memory used to store digital information.Image recorder 72 is coupled to memory 74 via data line 76. Controller68 may also control memory 74 and Image recorder 72 via control lines 78and 80.

[0035] Through the operation of camera 60, a collage of sharp areas maybe formed to make an image which is sharp at all points. For example, aseries of digital images of the same scene may be captured with Imagerecorder 72, each focused at a different distance. That is, controller68 causes motorized optics 64 to cycle through a range of focuses (e.g.,from 5 meters to infinity), image recorder 72 captures images of a scenetaken at different focuses, and memory 74 stores the captured images.The focus of motorized optics 64 can be varied continuously, or insteps, depending on conditions and the image required.

[0036] And further depending on conditions and the image required, oneto many hundreds of images may be captured. For example, if the image isentirely of a distant horizon, only a far focus image would be required.Therefore, the overall shutter speed may be very short.

[0037] Camera 60 may be a still camera or a video camera. Controller 68can be used to sequence motorized optics 64 through any range offocuses, as the desired range-of focuses may change with the type ofscene and lighting conditions. If camera 60 is used as a video camera,motorized optics 64 must be made to operate very quickly, as severalframes (each including several images taken at different focuses) persecond must be captured. To save time, controller 68 could be programmedto cycle motorized optics 64 from the closest desired focus to thefurthest desired focus to capture the images required to generate oneframe, and then cycle motorized optics 64 from the furthest desiredfocus to the closest desired focus to capture the images required togenerate the next frame. This process could then be repeated for allsubsequent frames.

[0038] The same segment of the scene in each of the digital imagesstored in memory 74 (say a 5×5 pixel array) may be sampled for contrast(the highest contrast corresponds to the sharpest focus). Each 5×5 highcontrast segment may then be assembled into a single image which will besubstantially in focus over the entire scene. This may be done with moreadvanced software algorithms which will recognize “continuous shapes” orobjects to simplify the process and make it more rapid. The manipulationis most easily carried out in digital form (either from digitized analogoriginals or from digital originals) but may also be done in an analogformat (cut and paste).

[0039] Referring now to FIG. 1, a preferred embodiment of the presentinvention is illustrated. Objects 15A-15C represent the position ofseveral objects in space as perceived by a viewer 20. Objects 15A-15Care distances 22A-22C, respectively, away from viewer 20. Objects15A-15C also reflect light cones 16A-16C towards viewer 20. As discussedabove, the degree to which a light cone 16 is diverging when it reachesviewer 20 varies with the distance of an object 15 from viewer 20. Torecreate a 3D image of objects 15A-15C, an image 10 (which is preferablyperceived as sharp over its entire area) is placed in registeredalignment with an array 12 of micro-lenses 14. However, the preferredembodiment can also operate on an image 10 that is not sharp at eachpoint.

[0040] Array 12 can be a substantially flat two dimensional array, or itcan be an array having a desired degree of curvature or shape, whichdepends on the curvature or shape of image 10. The characteristics ofeach micro-lens 14 corresponding to each point or pixel on image 10 arechosen based on the focus distance of the camera lens which made thatpoint or pixel of the image sharp. The focal lengths of the micro-lenses14 may be chosen so that light cones 18A-18C duplicate light cones16A-16C (based on the expected or known viewing distance from themicro-lenses, or based on a relative scale or an arbitrary scale to varythe perceived image). In this respect, viewer 20A will see the same 3Dimage seen by viewer 20.

[0041] Since image 10 can be viewed as a coherent 2D image when viewedby itself, the appearance of image 10 can be made to vary or alternatebetween 2D and 3D. If 2D viewing is desired, lenses 14 in array 12 caneither be removed, or can be adjusted to be optically neutral. If 3Dviewing is desired, lenses 14 in array 12 can be adjusted as describedabove.

[0042] A similar procedure may be utilized to produce 3D motionpictures/video. As is known to those skilled in the art, motion video isachieved by rapidly displaying images in sequential fashion. Therefore,sequential images in focus over the entire image (or to the degreedesired) must be created. To achieve this, a video camera which is madeto rapidly and continuously cycle between near and far focus is used.Each overall sharp image is produced by the techniques discussed above(utilizing depth of field, knowledge of the scene, collage techniques,etc.). Further, intelligent software can be used in combination withstill or video cameras to optimize depth of field, number of focus stepson a focus cycle, etc., based on ambient conditions, previously inputtedpreferences, and/or the past (immediately prior or overall past history)appropriate settings. Additional software/hardware manipulation can beused to make sharp images over the entire scene or to the degreedesired. For example, the periphery of a scene may be selectively out offocus.

[0043] Although the overall field of view of the human eye is large, thebrain focuses on a central portion and the periphery is oftensubstantially out of focus. In the ideal case the image behind themicro-lens array is sharp over the entire scene so that as the viewerexamines different portions of the scene each will come into focus asthe viewer focuses properly. There are, however, situations in whichsharpness over the entire image is not needed, such as in videosequences when the viewer only follows a particular field within ascene.

[0044] Once the desired video images are captured, 3D display isachieved by placing the images behind an array 12 of variable focuslenses 14, as discussed above with respect to FIG. 1. In each frame inthe video sequence, for each point or pixel of the frame there is acorresponding focus setting for the lens 14 which is in register withthat pixel. As each frame is sequentially displayed each pixel variesits focus to the appropriate predetermined setting for the pixel of thatframe.

[0045] Since each point or pixel has with it an associated lens orcompound lens, the rays from each pixel can be controlled to reach theeye at a predetermined angle corresponding to the 3D depth desired forthat pixel. There may be multiple lens designs which may suit thedesired effect for any given situation.

[0046] Referring again to FIG. 2, an important consideration in theoperation of the present invention is the eye to pixel distance.Different lens designs are required for close screens such as goggles(see FIG. 2(b)) than are required for more distant screens (see FIG.2(c)). As is depicted in FIG. 2(b) (medium and far focus), there aresituations where combinations of elements (such as a positive and anegative lens) can be moved relative to each other to create the desiredoptical effect. Thus, in one embodiment, multiple arrays could be movedrelative to each other to create the proper light output. For a morecomplete description of the properties of combinations of opticalelements, see, e.g., Ray (cited above), pp. 43-49, which is alsoincorporated herein by reference.

[0047] Consider the analogous behavior of a point of diffuse reflectionand a point of focus from a lens; if both the point of focus and thepoint of reflection are at the same distance from the eye, the angle ofthe rays upon reaching the eye will be the same. Because the pupil ofthe eye is relatively small, about 5 mm, only a small fraction of thediffusely reflected light cones are observed by the eye, and one doesnot need to “recreate” rays which are not observed by the eye.

[0048] The above described techniques may be used for display screenssuch as television, video, video cameras, computer displays, advertisingdisplays such as counter top and window displays, billboards, clothes,interior decorating, fashion watches, personal accessories, exteriors,camouflage, joke items, amusement park rides, games, virtual reality,books, magazines, postcards and other printed material, art, sculptures,lighting effects which cause light to become more intense or diffuse, asmay be desired in photographic or home use applications, and any otherapplications where three dimensional or variable optical effects aredesired.

[0049] Computer displays are typically placed close to a user, and theuser's eyes are constantly set at a single distance which puts strain onthe eye muscles. To prevent eyestrain and long-term deleterious effects,it is recommended that one periodically look at distant objects. Byusing the present invention, a lens array can be adjusted so that theviewer can focus near or far to view the display. Such variation inapparent viewing distance (the display itself may be kept at the samedistance) may be manually user controlled, or may follow a predeterminedalgorithm (such as slowly and imperceptibly cycling but moving through arange to prevent strain). Such algorithms may also be used fortherapeutic purposes. The viewing distance may be modulated totherapeutically benefit certain muscle groups. The technique may be usedfor books as well as other close-field intensive work.

[0050] One application of the still 3D images, according to the presentinvention, would be in the field of fine art and collectibles. Moreover,still images may be paired with fixed focal length lens arrays as wellas variable focus arrays. Unique effects can be achieved by modulatingthe focal length of the lenses in conjunction with a still image.Eccentric art as well as eye-catching displays or advertisements couldbe achieved by undulating the focus of a still image. In particular,this technique can be used to guide the viewer's attention to particularportions of an image by selectively modulating the apparent viewing areaof interest and leaving the rest of the image static—or vice versa, oralter the focus of a region and its apparent size. For example, if thesize of an object (in terms of its percentage of an observer's field ofview) stays the same, and the observer's eye switches from near focus tofar focus, then the observer's sense of how large the object is willchange (i.e., the observer will perceive the object as being bigger).Similarly, if the size of an object (in terms of its percentage of anobserver's field of view) stays the same, and the observer's eyeswitches from far focus to near focus, then the observer will perceivethe object as being smaller). This effect is further aided by including“reference” images—images of objects of known size. Therefore, such ascreen could selectively cause changes in apparent size, for example, tograb the observer's attention.

[0051] Wrap-around, or all encompassing views are advantageous becausethey eliminate distracting non-relevant peripheral information andimages. There are two general techniques for giving the viewer an allencompassing view of a scene. The first is to use extremely large and/orcurved viewing screens most useful for group viewing (e.g. the Sony IMAXtheaters or a planetarium). The second technique is the use ofindividual viewing goggles or glasses. In this technique relativelysmall screens are placed close to the eyes. An advantage to using themicro-lenses is that even at very close distances, it is difficult forthe average person to discern features of less than 100 microns—so ifthe micro-lenses in the array are made small enough (but are largeenough so that unwanted diffraction effects do not predominate) thescreen can remain virtually continuous without pixel effects. Becausethe screens are small, reductions in cost to achieve the wrap-around allencompassing views are achieved. Additionally, it is possible to useblackened areas around the screen if the screen does not fill the entireviewing angle so as to remove distractions. Alternatively, someapplications would advantageously incorporate external visual images.For example, a partially transparent display could overlap images fromthe environment with displayed images (this can be used in otherembodiments such as heads up displays). Such displays could havemilitary as well as civilian use. In particular, information can bedisplayed to operators of moving vehicles. When using goggles, suchdisplays could be visible to one eye or both.

[0052] If a computer display were generated within wrap-around goggles,the effective screen size would be maximized. There is a trend towardsincreasing monitor sizes for computers as the total information/numberof computer applications simultaneously running increases. A wrap-aroundgoggle computer display would allow the user to use his entire field ofvision as a desktop. This could be combined with 3D effects as well asthe strain reducing features described above.

[0053] Additionally, goggles may have one screen for each eye. Suchgoggles would require appropriate parallax correction so that the twoimages coincide and are perceived as a single image by the viewer. Anadvantage of using two screens is that the individual screens may beplaced very close to their respective eyes. The two images of differentparallax may be obtained from a variety of modified camera systems (seeRay, FIG. 65.10, Section 65.5 (cited above)). Alternatively, softwarealgorithms may be used to generate second images from single views withaltered parallax. Two screen goggles may also be used without parallaxcorrected images—that is, with the same perspective displayed to botheyes. This would likely result in some loss of natural 3D effect.However, many factors contribute to 3D effects, of which parallax isonly one.

[0054] Referring again to FIG. 1, the display 10 behind the lens array12 may be analog or digital, and it may be printed, drawn, typed, etc.It may be a photograph or transparency, in color or black and white, apositive or negative, inverted or offset by any angle or properlyoriented in its original fashion—it may emit or reflect light of manydifferent wavelengths visible or non-visible. It may be lithograph,sequential cinematic images and may be an XY plane in two or threedimensions. It may be a CRT, LCD, plasma display, electrochromicdisplay, electrochemiluminescent display or other displays well known inthe art.

[0055] Lenses 14 in array 12 may vary in terms of:

[0056] Size; preferably ranging from 1 cm to 1 micron.

[0057] Shape; preferably circular, cylindrical, convex, concave,spherical, aspherical, ellipsoid, rectilinear, complex (e.g. Fresnel),or any other optical configuration known in the art.

[0058] Constitution; the lenses may be primarily refractive, primarilydiffractive, or a hybrid diffractive-refractive design, such as thedesign disclosed in Missig et al., 1995, “Diffractive optics Applied toEyepiece Design,” Applied Optics 34(14):2452-2461, which is incorporatedherein by reference.

[0059] Number of lenses in the array; the arrays may range from 2×2 to avirtually unlimited array, as the lens array 12 could be in the form ofa very large sheet.

[0060] The number of lens elements used for each ‘pixel’; as is known inthe art, compound lenses may be useful for correcting opticalaberrations and/or useful for different optical effects. For example,spherical or chromatic aberrations may be corrected and zoom lens opticsmay be incorporated into an array. Moreover, one could use a fixed focusarray in front of a display and then a zoom array on top of the firstarray. Or in different applications different optical element designscould be incorporated into the same array.

[0061] Color of the lenses; the lenses may be colored or colorless andmay be transparent to a variety of visible and non-visible wave lengths.For example, stacked arrays of red, green, and blue lenses may be used.Alternatively, colored display pixels could be used with non-coloredlenses.

[0062] Composition of the lenses; as discussed above, the lenses may becomposed of a variety of materials in a variety of states. The lensesmay be liquid solutions, colloids, elastomers, polymers, solids,crystalline, suspensions etc.

[0063] Lens compression, relaxation, and deformation; the lenses may bedeformed by electrical and/or mechanical (e.g. piezoelectric) means.-Deformation may be employed to control effective focal length and/or tovary other optical properties of the lens or lens system (e.g.aberrations or alignment—alignment may be between lenses and/oralignment with the display)

[0064] Finally, arrays may be combined or stacked to vary or increasedifferent optical properties. The arrays can be curved or flat.

[0065] Many other various elements can be included in the preferredembodiments. For example, filters may be used in the arrays, between thearray and the display, and in front of the array. Such filters may beglobal, covering all or most pixels, or may be in register with only onepixel or a select group of pixels. Of particular note are neutraldensity filters (e.g. an LCD array). Other filters include colorfilters, gradient filters, polarizers (circular and linear) and othersknow to those skilled in the art.

[0066] Further, the surfaces of the different components of theinvention may be coated with a variety of coatings, such as, antiglarecoatings (often multilayer). Other coatings provide scratch resistanceor mechanical stability and protection from environmental factors.

[0067] Light baffling structures or materials may be used to preventunwanted stray light or reflections. For example, it may be desirable toisolate each pixel optically from neighboring pixels. In one embodiment,SAMs may be used to form micro light baffles. For example, micro-lenseswhich occupy hydrophilic regions may be circumscribed by hydrophobicregions whose surfaces are selectively occupied by light absorbingmaterial. Alternatively, micro-machined light baffle structures may beused.

[0068] The components of the invention may advantageously have varyingoptical properties. For some applications substantially transparentcomponents and support materials would be used—e.g. for use in a headsup display. In other cases, mirrored surfaces may be desirable—e.g. as abacking to maximally utilize reflected light and also for the use ofmirrored optical elements. Other materials include semitransparentmirrors/beam splitters, optical gratings, Fresnel lenses, and othermaterials known to those skilled in the art.

[0069] Shutters and/or apertures may be placed in various locations thesystem and may be global or specific (as the filters above). Shuttersmay be useful, for example, if a film based cinematic video scene wereused as the display. Apertures could be used to vary light intensity anddepth of field.

[0070] The overall systems may vary in size between a few microns andhundreds of meters or more. The system may be curved or flat. It may bea kit. It may be a permanent installation or it may be portable. Screensmay fold or roll for easy transportation. The screens may have coversfor protection and may be integrated into complex units (e.g. a laptopcomputer). The system may be used in simulators and virtual realitysystems. The system can be used as a range finder by correlatingeffective focus on the array with a plane of focus in the environment.The system may be used for advanced autofocus systems. For example, thesystem could be used to rapidly find optimal focus since the micro-lenscan focus much faster than a large mechanical camera lens and then thelens can be set to the accurate focus. The system can be used fordirectional viewing of a display—for example by using long effectivefocal lengths. The systems may also be disposable.

[0071] An important consideration in the present invention is the typeand direction of lighting. The lighting may be from the front(reflected) or from the rear (backlit) and/or from a variety ofintermediate angles. There may be one light source or multiple lightsources. In some cases both reflected and luminous backlighting aredesirable to more accurately represent a scene. For example, whenindoors looking out a window, one may perceive strong backlightingthrough the window and reflected softer light with directional shadowswithin the room. Combining backlight, reflected light and theintensity/neutral density filtering will give a more realistic image.Directional reflected light may be focused on a single pixel or specificarea or may be global (as with backlighting). The light may be filtered,polarized, coherent or non-coherent. For example, the color temperatureof sunlight varies through the day. A sunlight corrected source lightcould then be filtered to represent the reddish tones of a sunset imageetc. The light may be placed in a variety of positions (as with thefilters above) and may be from a variety of known light sources to oneskilled in the art including incandescent, halogen, fluorescent, mercurylamps, strobes, lasers, natural sunlight, luminescing materials,phosphorescing materials, chemiluminescent materials,electrochemiluminescent etc. Another embodiment is that of luminescinglenses. Liquid lenses or lenses which may be suitably doped withluminescent materials may be useful, especially in disposable systems.For example, consider a liquid phase lens resting on an electrode. Sucha lens (if it contained an ECL tag) could be caused to luminesce.

[0072] The present invention has been described in terms of a preferredembodiment. The invention, however, is not limited to the embodimentdepicted and described. Rather, the scope of the invention is defined bythe appended claims.

What is claimed is:
 1. A three dimensional imaging system comprising: atwo dimensional array of micro-lenses, at least some of the lenseshaving a variable focal length; and a two dimensional image having aplurality of image points or pixels; at least one micro-lens in thearray in registered alignment with one or more of the image points orpixels.
 2. A three dimensional imaging system comprising: a twodimensional array of variable focal length micro-lenses; and a twodimensional image having a plurality of image points or pixels; at leastone micro-lens in the array in registered alignment with one or more ofthe image points or pixels.
 3. A three dimensional imaging systemcomprising: an array of micro-lenses, at least some of the lenses havinga variable focal length; and an image having a plurality of image pointsor pixels; each image point or pixel in registered alignment with one ormore micro-lenses in the array.
 4. The invention of claim 3 wherein theimaging system is sold as a kit.
 5. The invention of claim 3 wherein theimaging system is incorporated in a pair of goggles.
 6. The invention ofclaim 3 wherein the imaging system is incorporated in a transparentheads-up display.
 7. The invention of claim 3 wherein the image has adepth of field greater than that which could be taken at any one focusdistance.
 8. The invention of claim 3 wherein the imaging system canalternate between 3D and 2D images.
 9. The invention of claim 8 whereinthe micro-lenses can be made optically neutral.
 10. The invention ofclaim 8 wherein the micro-lenses can be removed.
 11. The invention ofclaim 3 wherein the imaging system is incorporated in art work.
 12. Theinvention of claim 3 wherein the imaging system is incorporated inadvertisements.
 13. The invention of claim 3 wherein the imaging systemis incorporated in a virtual reality device.
 14. A three dimensionalimaging system comprising: a first array of micro-lenses, at least someof the lenses in the first array having a variable focal length; asecond array of micro-lenses, at least some of the lenses in the secondarray having a variable focal length; and an image having a plurality ofimage points or pixels; each image point or pixel in registeredalignment with one or more micro-lenses in the first array; at least onemicro-lens in the second array in registered alignment with one or moremicro-lenses in the first array.
 15. A three dimensional imaging systemcomprising: an array of variable focal length micro-lenses; and an imagehaving a plurality of image points or pixels; each image point or pixelin registered alignment with one or more micro-lenses in the array. 16.A three dimensional optical system comprising: an array of micro-lenses,each micro-lens having a fixed but individually predetermined focallength, the micro-lenses in the array having a plurality of focallengths; and an image having a plurality of image points or pixels; eachimage point or pixel in registered alignment with one or moremicro-lenses in the array.
 17. A three dimensional optical systemcomprising: an array of micro-lenses, each micro-lens having a fixedfocal length; and an image having a plurality of image points or pixels;each image point or pixel in registered alignment with one or moremicro-lenses in the array.
 18. A three dimensional optical systemcomprising: an array of micro-lenses, each micro-lens having a fixed butindividually predetermined focal length; and an image having a pluralityof image points or pixels; each image point or pixel in registeredalignment with one or more micro-lenses in the array.
 19. A threedimensional optical system comprising: an array of micro-lenses, eachmicro-lens having a fixed but individually predetermined focal length;and an image having a number of image points or pixels; at least onemicro-lens in registered alignment with one or more image point orpixel.
 20. An optical system for varying the apparent distance of acomputer screen, comprising: an array of variable focal lengthmicro-lenses; and a computer screen having a plurality of pixels; eachpixel in registered alignment with one or more micro-lenses in thearray.
 21. In an optical system comprising an array of variable focallength micro-lenses and a computer screen having a plurality of pixelsin registered alignment with one or more micro-lenses in the array, amethod for reducing eyestrain comprising the step of: periodicallyvarying the focal length of all of the micro-lenses in the array,whereby the computer screen appears to become closer or further away.22. In an optical system comprising an array of variable focal lengthmicro-lenses and a computer screen having a plurality of pixels inregistered alignment with one or more micro-lenses in the array, amethod for reducing eyestrain comprising the step of: periodicallyvarying the focal length of a subset of the micro-lenses in the array,whereby a portion of the computer screen appears to become closer orfurther away.
 23. An optical system for varying the apparent distance ofa computer screen, comprising: an array of variable focal lengthmicro-lenses; and a computer screen having a plurality of pixels; atleast one micro-lens in registered alignment with one or more pixels.24. An optical system for varying the apparent distance of a twodimensional object, comprising: an array of variable focal lengthmicro-lenses; and a two dimensional object having a plurality of pointsor pixels; each point or pixel in registered alignment with one or moremicro-lenses in the array.
 25. An optical system for varying theapparent distance of a two dimensional object, comprising: an array ofvariable focal length micro-lenses; and a two dimensional object havinga plurality of points or pixels; at least one micro-lens in registeredalignment with one or more points or pixels.
 26. An optical system forvarying the apparent distance of a two dimensional object, comprising:an array of fixed focal length micro-lenses; and a two dimensionalobject having a plurality of points or pixels; each point or pixel inregistered alignment with one or more micro-lenses in the array.
 27. Anoptical system for varying the apparent distance of a two dimensionalobject, comprising: an array of fixed focal length micro-lenses; and atwo dimensional object having a plurality of points or pixels; at leastone micro-lens in registered alignment with one or more points orpixels.
 28. A method for generating a three dimensional image,comprising the steps of: generating a two dimensional image having highdepth of field and having a number of image points or pixels; andprojecting light reflected from or emitted by each of the image pointsor pixels so as to generate a cone of light having a predetermined solidangle, the solid angle varying with the perceived distance of the imagepoint or pixel from a viewer.
 29. A method for generating a threedimensional image, comprising the steps of: generating a two dimensionalimage having high depth of field and having a number of image points orpixels; and reflecting, transmitting, or emitting light from each of theimage points or pixels so as to generate a cone of light having apredetermined solid angle, the solid angle varying with the perceiveddistance of the image point or pixel from a viewer.
 30. A method forgenerating a three dimensional image, comprising the steps of:generating a two dimensional image having a number of image points orpixels, the image being substantially in focus over a predeterminedarea; and projecting light reflected from or emitted by each of theimage points or pixels so as to generate a cone of light having apredetermined solid angle, the solid angle varying with the perceiveddistance of the image point or pixel from a viewer.
 31. A method forgenerating a three dimensional image, comprising the steps of:generating a two dimensional image having a number of image points orpixels, the image being substantially in focus over a predeterminedarea; and reflecting, transmitting, or emitting light from each of theimage points or pixels so as to generate a cone of light having apredetermined solid angle, the solid angle varying with the perceiveddistance of the image point or pixel from a viewer.
 32. A method forgenerating optical effects, comprising the steps of: generating a twodimensional image having a number of image points or pixels; andprojecting light reflected from or emitted by each of the image pointsor pixels so as to generate a cone of light having a variablepredetermined solid angle.
 33. A method for generating optical effects,comprising the steps of: generating a two dimensional image having anumber of image points or pixels; and reflecting, transmitting, oremitting light from each of the image points or pixels so as to generatea cone of light having a variable predetermined solid angle.
 34. Amethod for generating a three dimensional image, comprising the stepsof: generating a two dimensional image having high depth of field andhaving a number of image points or pixels; and projecting lightreflected from or emitted by each of the image points or pixels so as togenerate a cone of light having a variable predetermined solid angle.35. A method for generating a three dimensional image, comprising thesteps of: generating a two dimensional image having high depth of fieldand having a number of image points or pixels; and reflecting,transmitting, or emitting light from each of the image points or pixelsso as to generate a cone of light having a variable predetermined solidangle.
 36. A method for generating a three dimensional image, comprisingthe steps of: generating a two dimensional image having a number ofimage points or pixels, the image being substantially in focus over apredetermined area; and projecting light reflected from or emitted byeach of the image points or pixels so as to generate a cone of lighthaving a variable predetermined solid angle.
 37. A method for generatinga three dimensional image, comprising the steps of: generating a twodimensional image having a number of image points or pixels, the imagebeing substantially in focus over a predetermined area; and reflecting,transmitting, or emitting light from each of the image points or pixelsso as to generate a cone of light having a variable predetermined solidangle.
 38. A method for generating a three dimensional image, comprisingthe steps of: generating a two dimensional image using an optical systemhaving a large depth of field, the image having a number of image pointsor pixels; and projecting light reflected from or emitted by each of theimage points or pixels so as to generate a cone of light having avariable predetermined solid angle.
 39. A method for generating achanging three dimensional image using a variable focus micro-lensarray, comprising the steps of: generating a sequential series of twodimensional images that are substantially in focus over a predeterminedarea, the images having a number of image points or pixels; projectinglight reflected from or emitted by each of the image points or pixelsthrough the micro-lenses in the array so as to generate a cone of lighthaving a predetermined solid angle, the solid angle varying with theperceived distance of the image point or pixel from a viewer; andvarying the focal length of each micro-lens in the array as appropriatewith each sequential image.
 40. A three dimensional imaging systemcomprising: an array of variable focal length liquid micro-lenses formedon a SAM; and an image having a plurality of image points or pixels;each the image point or pixel in registered alignment with one or moremicro-lenses in the array.
 41. A three dimensional imaging systemcomprising: an array of variable focal length liquid micro-lenses formedon a SAM; and an image having a plurality of image points or pixels; atleast one micro-lens in the array in registered alignment with one ormore image points or pixels.
 42. The method of claim 41 wherein themicro-lenses are liquid lenses adherent to one or more SAMS.
 43. Themethod of claim 42 wherein the focal lengths of the liquid lenses areadjusted by the application of an electric field.
 44. The method ofclaim 41 wherein the micro-lenses are flexible lenses.
 45. The method ofclaim 44 wherein the focal lengths of the flexible lenses are adjustedby elastic deformation.
 46. The method of claim 45 wherein the elasticdeformation is caused by pressure exerted by a piezoelectric element.47. A three dimensional imaging system comprising: a first array ofmicro-lenses, at least some of the lenses in the first array having avariable focal length and being colored; a second array of micro-lenses,at least some of the lenses in the second array having a variable focallength and being colored; a third array of micro-lenses, at least someof the lenses in the third array having a variable focal length andbeing colored; and an image having a plurality of image points orpixels; each image point or pixel in registered alignment with one ormore micro-lenses in the first array; at least one micro-lens in thesecond array in registered alignment with one or more micro-lenses inthe first array; at least one micro-lens in the third array inregistered alignment with one or more micro-lenses in the second array.48. The three dimensional imaging system of claim 47 wherein the lensesin the first array are colored red, the lenses in the second array arecolored green, and the lenses in the third array are colored blue.